The present invention relates to a signal distribution system and method based on a bus arrangement and, more particularly, to a signal distribution system and method based on a bus arrangement comprising an address bus, a data bus, a control bus, and the like.
Conventionally, there are devices called system LSIs (Large Scale Integrated Circuits) in which not only a CPU but also interfaces of memory devices such as a DRAM (Dynamic Random Access Memory) and a ROM (Read Only Memory) and functional units such as an MPEG (Moving Picture image coding Experts Group) decoder are integrated on one chip. In such a system LSI, the functional blocks including a CPU are connected through an address bus, a data bus, a control bus, and the like. The buses are driven and controlled by a bus control circuit formed on the same chip.
FIG. 12 shows a bus arrangement in a conventional system LSI.
As shown in FIG. 12, a plurality of functional blocks A to F are arranged on a chip in accordance with their functions. In this case, the block A is a CPU 1, the block B is a debug unit 2, the block C is an MPEG decoder 3, the block D is another functional unit 4 such as a graphic engine, the block E is a DRAM interface 5, and the block F is a ROM interface 6. In addition to the functional blocks A to F, a bus signal distribution block 7 and a bus control circuit 8 are integrated on the same chip.
With this arrangement, various bus signals such as an address signal, a data signal, and a control signal output from the functional blocks A to F are temporarily collected by the bus signal distribution block 7 and then distributed to the desired functional blocks A to F through common buses such as an address bus 10, a data bus 11, and a control bus 12. Distribution of bus signals is controlled by the bus control circuit 8.
Details of the arrangement of the bus signal distribution block 7 will be described.
The bus signal distribution block 7 has a plurality of distribution blocks in correspondence with the types of connected buses. In this case, the bus signal distribution block 7 has an address signal distribution block 71, a data signal distribution block 72, a control signal distribution block 73, an address valid signal distribution block 74, a read/write signal distribution block 75, and an address ready signal distribution block 76.
The input sides of these distribution blocks 71 to 76 are connected to the plurality of buses from the functional blocks A to F, and the output sides are A connected to the common buses such as the address bus 10, data bus 11, and control bus 12. Although not illustrated, bus connection to the address valid signal distribution block 74 and read/write signal distribution block 75 has the same arrangement as that of bus connection to the address signal distribution block 71, and bus connection to the address ready signal distribution block 76 has the same arrangement as that of bus connection to the control signal distribution block 73.
Signals output from the distribution blocks 71 to 76 are transmitted to the desired functional blocks A to F through the common buses.
Signal transmission/reception by the functional blocks A to F is performed in the following way.
Address signals output from the functional blocks A, B, C, and D are input to the address signal distribution block 71. After this, one of the signals is selected under the control of the bus control circuit 8. The selected address signal is input to one of the functional blocks A to F, which corresponds to the address. At this time, the address signal distribution block 71 drives the entire address bus 10 commonly connected to the functional blocks B to F to input the signal to a desired functional block, as shown in FIG. 13.
Data signals output from the functional blocks A to F are input to the data signal distribution block 72, and then, one of the signals is selected under the control of the bus control circuit 8. The selected data signal is input to one of the functional blocks A to F, which is designated by an address signal in advance. At this time, the data signal distribution block 72 drives the entire data bus 11 commonly connected to the functional blocks A to F to input the signal to a desired functional block, as shown in FIG. 14.
Control signals from the functional blocks B to F are input to the control signal distribution block 73. After this, one of the signals is selected under the control of the bus control circuit 8. The selected control signal is input to one of the functional blocks A to F, which is designated by an address signal in advance. At this time, the control signal distribution block 73 drives the entire control bus 12 commonly connected to the functional blocks A to D to input the signal to a desired functional block, as shown in FIG. 15.
That is, the types of signals input/output to/from the functional blocks A to F are determined in accordance with the functions of the functional blocks A to F. For example, since the functional block A comprises a CPU, an address signal is output, and a data signal is input or output, although no address signal is input.
Since the functional blocks B, C, and D comprise peripheral functional units such as a debug unit and an MPEG decoder, both address signals and data signals are input or output.
The functional blocks E, and F comprises interfaces of memory devices such as a DRAM and a ROM, address signals are input but not output. A data signal is input/output to/from the functional block E to read/write data. However, the functional block F is used to merely read out a data signal, so the data signal is only output.
However, in the above-described prior art, the entire common bus must be driven only to input a signal to one functional block, resulting in an increase in power consumption.
The conventional arrangement still has an advantage that the circuit arrangement is simple because all functional blocks are connected to one common bus. However, along with today""s development in micropatterning, wiring can be more easily led, and a demand has arisen more for reduction of power consumption during operation than for a simple circuit arrangement.
It is an object of the present invention to provide a signal distribution system and method based on a bus arrangement for reducing power consumption.
In order to achieve the above object, according to the present invention, there is provided a signal distribution system comprising a plurality of functional blocks divided into a plurality of groups each of which receives bus signals of the same type, at least one bus signal distribution block for distributing a bus signal received from a transmission source functional block to a transmission destination functional block, at least one bus connected between the bus signal distribution block and the functional blocks, the bus having division buses arranged in units of groups of the functional blocks, and bus control means for controlling the bus signal distribution block to select one of the division buses connected to a transmission destination group on the basis of an address signal received from the transmission source functional block and transmit the received bus signal to the transmission destination functional block in the transmission destination group through the selected division bus.